Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
A typical cellular wireless network includes a number of cellular base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which wireless communication devices (WCDs) (also known as user equipment devices (UEs)), such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices, can operate. In turn, each cellular base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. To facilitate this, each cellular base station may have one or more base station antennas that radiate to provide wireless coverage to WCDs.
To provide wireless coverage, base stations are often arranged in a typical configuration in which one or more base station antennas are positioned outdoors at a tower-top. These base station antennas are connected to base station receivers and transmitters. This arrangement of base station antennas, receivers, and transmitters allows the base station to communicate with WCDs within the coverage area of the base station. When, for example, a base station transmitter provides a signal to a base station antenna, the base station antenna radiates that signal over its coverage area. This signal may be received by one or more WCDs within the coverage area. Similarly, WCDs within the coverage area may transmit a signal that is received by the base station via the base station antenna and receiver.
Each base station antenna has an expected radiation pattern that is based on the design characteristics of the antenna. Base stations usually have directional antennas that are designed to radiate energy in a particular direction; this direction is known as the forward direction. Due to their directional design, directional antennas exhibit peak gain in the forward direction.
Base stations often use a particular type of directional antenna known as sector antenna. Sector antennas are designed to have a fan-shaped radiation pattern covering, for example, 60°, 90°, or 120° of arc in the horizontal (or azimuth) plane and a narrow pattern in the vertical (or elevation) plane. The sector, or main beam, of the antenna (e.g. 60°, 90°, or 120°) is usually defined by the −3 dB beam width in the azimuth plane, where the beam width is measured relative to the peak gain. Sector antennas have significant signal strength (or gain) within their sector and exhibit diminishing signal strength at angles further from the forward direction.
To provide continuous wireless coverage in multiple directions away from the base station, multiple base station antennas are often laid out in an antenna array. To provide 360° coverage in the horizontal plane, a base station may have multiple sector antennas spaced around the circumference of a tower-top. Or, a base station may have base station antennas arranged in an array to provide wireless coverage in particular directions.
Base stations are often deployed repeatedly over a wide geographical area such that each base station, or cell, covers a certain geographical area, or cell sector, until the wide geographical area is covered by cell sectors. Since a wireless coverage area may consist of many base stations each having an array of antennas, the number of individual base station antennas within a coverage area can be very extensive.